In regard to the different sound of cables I think much of this has to do with their construction and material.
With regard to balanced operation, the statement is mostly false. However it is widely believed by many in high end audio. "Mostly" as in: as long as the cable has an adequate shield with a twisted pair within for the signal, then other construction details and materials will be rendered moot.
However as I mentioned before if the standards of the balanced line system are *not* observed then the above-quoted statement is true.